This invention relates to scanning display methods and apparatus, and more particularly to a scanning display including an array of optical elements, such as microlenses.
Small, light weight displays are desirable for use in portable devices such as cellular phones, pagers, handheld computers and helmet-mounted displays. One challenge to implementing a small lightweight display is the typically poorer resolution achieved relative to that of a full size computer screen display. A scanned beam display such as the virtual retinal display disclosed in U.S. Pat. No. 5,467,104 to Furness et al, which is incorporated herein by reference, is able to achieve improved resolution while being of a relatively small volume.
A scanned retinal display device is an optical device that produces a preceived image by scanning a modulated beam of light onto the retina of an eye. In one such device, light is emitted from a light source, passed through a lens, then deflected along a scan path by a scanning device. At a distance defined by the lens, the scanned light converges to a focal point for each pixel position. As the scanning occurs the focal point moves to define an intermediate image plane. The light then diverges beyond the plane. An eyepiece typically is positioned along the light path beyond the intermediate image plane at some appropriate position. The eyepiece receives light that is being deflected along a raster pattern and redirects the beam to define an "exit pupil." The exit pupil occurs shortly beyond the eyepiece in an area where a viewer's eye pupil is to be positioned. When a viewer looks into the eyepiece to view an image, the viewer's eye pupil receives the light at differing angles at different times during the scanning cycle. This range of angles determines the size of the image perceived by the viewer. Modulation of the light during the scanning cycle determines the content of the image.
The scanned retinal display typically places significant demands upon the scanning system, in terms of field of view, speed of the scanning mirror, size, temperature dependence, and a variety of other performance and design parameters. Often, scanned beam systems meet these demands with scanned mirrors that move at high angular rates. While scanned mirror display systems can perform well, it is sometimes desirable to develop alternative approaches to producing displays using scanned beams, particularly in light weight, small volume displays. As disclosed herein, an approach to producing such an image includes display that generates an image upon a screen or viewer's eye using a microlens array and a light source array.